Search Results

Vehicle to vehicle sideswipe collisions may involve contact between a vehicle body and a contacting vehicle's rotating wheels, tires and lug nuts. During a sideswipe collision between a truck and an automobile it is not uncommon to see lug marks in the shape of consecutive damage loops or strikes on the side of the impacted vehicle. The damage loops or strikes are generated by the protruding lug nuts of the truck wheel as it passes by the impacted vehicle at a shallow angle. Additionally, rubber transfers due to contact with the tire sidewall and metal scraping from the wheel rim also leave distinctive shapes on the sides of the contacted vehicle body. The tire, rim, lug nut markings and associated damage manifest themselves as a special case of the epitrochoid and can be geometrically and mathematically described. Presented is a derivation of the equations that govern the lug, rim and tire positions and relative motions.

Tire-roadway frictional drag, an important consideration for transportation accident reconstruction, is dependant on vehicle, roadway and environmental factors. Vehicle factors include vehicle specific properties such as geometry and inertial parameters, braking system type, tire size, and tire properties. Roadway factors include grade, pavement type, construction, pavement age, and other parameters. Environmental factors include temperature and inclement weather. In order to control these (and other) vehicle, roadway, and environmental factors, the determination of tire-roadway frictional drag is done through staged testing using an instrumented vehicle. Staged testing is typically performed with an exemplar vehicle on a similar roadway under comparable environmental conditions. Engineering instrumentation includes acceleration and velocity sensors as well as a brake gun to directly measure total braking distance.

Staged collision test data includes instrumentation in order to measure acceleration time histories, force time histories and other engineering parameters. The output from these instruments allows the analysis of vehicle energy absorption and collision pulse shape characteristics. Additionally, crash test repeatability, velocity sensitivity, and the influence of rigid versus deformable barriers may be investigated. The present study analyzes collision pulse shapes including analytical relationships and pulse parameters. Closed form functions are applied and compared to the observed experimental pulse shapes. Differences between analytical predictions and observed experimental results are explored. Techniques are presented whereby collision pulses can be analyzed and applied to the reconstruction of real world automobile collisions. The use of acceleration time histories and crash test data in the determination of vehicle structural characteristics is investigated.

This paper surveys some current technologies in reconstructing lateral narrow object impacts. This is accomplished through a multi-step process. First, staged crash test data is reviewed and presented in order to understand the observable vehicle structural deformation trends. A commonly used crush energy reconstruction algorithm (CRASH1) is then applied to the test data and an analysis is made of the application of this tool to this impact mode. The use of default structural parameters as used in CRASH 3 is also discussed. A linear and angular momentum analysis is developed in order to demonstrate closed form vehicle dynamics prediction methodologies for non-central lateral impacts. The momentum methods presented are compared to a commonly used impact simulation tool. Finally, change in velocity (ΔV) and the use and analysis of ΔV for lateral pole impact reconstruction is discussed.

For many years, crash testing performed for the US Department of Transportation National Highway Traffic Safety Administration (NHTSA) has been used to analyze and study trends in the measured Anthropomorphic Test Device (ATD) test responses in 48 kph (FMVSS 208) and 56 kph (NCAP) frontal barrier crash tests. Although many variables must be controlled in these tests, the initial seated position of the dummy has been found to significantly affect the measured dummy parameters (head acceleration, chest acceleration, femur loads). Data generated from the NHTSA sponsored testing is archived in the NHTSA Vehicle Crash Test Database (VCTDB). The present study is performed to analyze the driver ATD positions in frontal crash tests. First, a publication review was performed from which selected related seating position literature is discussed. The resulting relationships to design guidelines (e.g. SAE J standards) are also discussed.

Impact induced vehicle residual deformation serves as a basis for the reconstruction engineer to make a determination of the energy absorbed during the impact phase of a collision. Many impact phase reconstruction algorithms assume a linear relation between an absorbed energy function and residual crush in order to derive collision severity (Delta V, BEV, etc.). This is done through the assumption of a constant spring stiffness value to describe the vehicle frontal impact stiffness. However, some recent rigid barrier impact test data has demonstrated non-linear trends between crash energy and residual crush. The total body of available crash test data indicates that vehicle frontal stiffness cannot be precisely modeled through the use of a single linear spring stiffness for all vehicles. This paper will explore stiffness trends and make comparisons to the previously assigned linear assumption for a diverse sample of vehicles and test speeds into frontal fixed barriers.

The concept of increasing strength requirements for automotive seats has been proposed as a means of reducing occupant injuries, particularly in the rear-end impact environment. This paper will evaluate various safety trade-offs and practical requirements of seat design brought about by modifications that include the rigidification of seat structures. Rigidified and yielding seat design concepts are evaluated, utilizing analytical procedures as well as data from static and dynamic tests. The effect of seat rigidification is examined in terms of occupant interaction with the surrounding structure and with the restraint system. Potential effects of these modifications on occupant kinematics and resulting injury exposures are also examined. The elastic properties of conventionally rigidified seat structures are compared to rigid seat structures in terms of their effect on occupant motion during collision.

The reconstruction of motor vehicle collisions requires an analysis and quantification of the impact phase of the vehicular collision. In order to study the dynamics and velocity dependence of the impact phase, a series of four rigid barrier impact tests were designed and conducted. These tests were structured to bracket publicly available government compliance test data for a specific make and model vehicle and to define the vehicle frontal crash response over a broad range of impact speeds. These tests also provide a basis for the analysis and comparison of the results of a common damage energy reconstruction technique. A car to car, front to rear, impact test using the same make and model vehicles, was conducted to allow the comparison of crush incurred in two different collision environments at similar Delta V (AV) exposure levels.